/Engine/Source/Runtime/Engine/Public/GeomTools.h
Triangulate a polygon. Check notes in implementation.
static bool TriangulatePoly ( [TArray](API\Runtime\Core\Containers\TArray)< FVector2D > & OutTris, const [TArray](API\Runtime\Core\Containers\TArray)< FVector2D > & PolygonVertices, bool bKeepColinearVertices )